1. Field of the Invention
The present invention generally relates to a touch panel, and more particularly to a touch panel with a multiple-ground ring design.
2. Description of the Related Art
Touch panels can be categorized as resistive type, capacitive type and optical type touch panels according to different sensing technologies. Due to advantages of the capacitive type touch panel, including quick response time, high reliability and durability, capacitive type touch panels have become the most widely used touch panel. Capacitive touch panels uses capacitive coupling effects to detect touch location. When conductive pointers such as user finger(s) approach or touch the surface of the capacitive type touch panel, capacitance(s) corresponding to the touch location(s) will be altered and thus the touch location(s) is able to be detected.
A typical capacitive type touch panel has electrodes and circuit traces formed by transparent conductive materials on a glass substrate. The circuit traces usually suffer damages resulting from electrostatic discharge (ESD) during manufacturing process or due to other causes. Capacitive type touch panels thus must have electrostatic discharge protection designs in order to avoid the damages caused by electrostatic discharge.
FIG. 1 shows a top view of a capacitive type touch panel. The capacitive type touch panel comprises a touch control area with electrodes and a grounding ring 12 surrounding the touch control area. The electrodes are connected in series along two directions perpendicular to each other to form an electrode matrix. The electrode matrix comprises a plurality of first electrodes 14 and traces 18 in one direction and a plurality of second electrodes 16, traces 19 and bridges 17 in another direction. Each bridge 17 electrically connects two adjacent second electrodes 16. The ground ring 12 surrounds the first and the second electrodes 14 and 16, the traces 18 and 19 and a junction area 11 to achieve electrostatic discharge protection.
Although the electrostatic discharge protection design set forth can provide certain electrostatic discharge protection capability, there s still a risk of rampant electrostatic charges cross the protection since the electrostatic discharge protection design set forth only deploys one ground ring on the peripheral region of the electrodes and traces. The electrostatic discharge current could jump into the traces adjacent the ground ring and cause damages of the traces or the electrodes.
Therefore, there is a need to provide an innovative touch panel to improve the shortcomings of the traditional touch panel.